Field of the Invention
The method of fabricating an active device and more particularly, to a method of fabricating a thin film transistor.
Description of Related Art
With the rise of awareness of environment protection in recent years, flat display panels benefiting from characteristics, such as low power consumption, good space efficiency, no radiation, high-quality and so on, have become mainstream in the market. The commonly seen flat display panels include liquid crystal displays (LCDs), plasma displays, electroluminescent displays and so on.
Taking the currently most popular LCDs for example, an LCD is mainly composed of a pixel array substrate, a color filter substrate and a liquid crystal layer sandwiched therebetween. A thin film transistor is commonly used as a switching element of each pixel structure on the pixel array substrate in the related art, and the performance of the switching element depends on the quality of an active layer of the thin film transistor. The active layer (e.g., a metal oxide semiconductor layer) of the thin film transistor has an issue of being easily damaged by ambient vapor during a process of patterning a source and a drain, which is unfavorable for the quality of the thin film transistor. In order to improve the issue, in a method of fabricating the thin film transistor in the related art, an etching stopper layer is first formed on the active layer of the thin film transistor, and a metal layer on the etching stopper layer is then patterned to form a source and a drain of the thin film transistor. Thereby, no matter whether the source and the drain are patterned and formed by a wet or a dry etching process, the active layer of the thin film transistor can be prevented from being damaged by the etchant used in the wet etching process or the plasma used in the dry etching process. In addition, the etching stopper layer covers at least a portion of an area of the active layer, the vapor can less contact the active layer, so as to reduce the probability of the active layer in an amorphous state deteriorating into a conductor. However, the disposition of the etching stopper layer causes some issues, such as the reduction of an aperture ratio of the pixel array substrate and the increase of fabrication cost of the thin film transistor.